Disposing of and effectively treating biowastes is an increasingly difficult problem.
The abundant open dumping space of yesterday is now probably someone's backyard. The sites now left are surrounded by someone's air, living, and working spaces and located above someone's drinking water. Everyone, it seems, wants waste in someone else's back yard.
Earth's capacity to absorb and civilization's ability to ignore waste behind a defense of rhetoric rather than action is very nearly at an end.
The axioms, sometimes self-serving, sometimes in hysterical response, that "dilution is the solution to pollution" and at the other extreme--"compaction is the action of satisfaction"--are foundations of heretofore employed waste management techniques. These approaches completely fail to take into consideration the simple fact that the problem of waste is not going to go away on its own accord. Endlessly diluting, compacting, transporting, storing, transmutating or apportioning waste to air, earth and water merely prolongs but makes more certain the ultimate reckoning.
One widely employed solution to the waste disposal problem is incineration of the offending material; another is controlled disposal and/or treatment of the waste in a digester, sanitary landfill, lagoon, compost pile, or the like.
Incineration is of limited value. Capital costs of the equipment required to incinerate all of the wastes generated in a metropolitan or other populous area is prohibitive. Los Angeles, as one example, is reported to generate 500,000 tons of solid waste daily. Incineration is also only a partial solution because non-combustible solids must often be sorted out and otherwise disposed of prior to incineration. Furthermore, complex and noxious emissions generated by incineration are difficult and expensive to control; and the solids generated in an incinerator (and often in an incinerator's stack gas scrubber) are wastes that must be transported to a landfill or other disposal site and stored. The location of acceptable sites for incinerators--especially those intended to accommodate body parts and other perhaps diseased biological wastes--is also a significant problem.
Because of the foregoing and other problems, landfills are still most often employed for solid waste disposal. Like incineration, this approach is not free of significant problems such as siting and the emission of noxious offgases including odorous and inodorous but toxic volatile compounds (VC's). Other problems associated with the disposal of solid wastes in landfills include: the formation of toxic, often highly corrosive leachates; the sheer bulk of the waste; and the control of disease vectors including insects; birds (sea gulls are now being observed in number in the Great Plains); rodents; and other animals such as raccoons, coyotes and the like. Also of concern is the loss of valuable raw material potentials such as plant and other nutrients found in many biological wastes.
Problems of the character discussed above are also appurtenant to many other waste generating and processing operations--composting processes, sewage digesters and lagoons, hospitals, septic tanks, feed lots, slaughterhouses, dairy herds and poultry flocks to name but a few.
These problems also exist in the collection, storage, and movement of biowastes from one point to another. Biochemical effluvia; bacteriologically contaminated garbage bags, cans, and dumpsters; and equally miasmatic garbage trucks, scows, sewer lines and other forms of waste transport prevail; and corrosive, toxic leachates are commonly present.
The same problems exist in the home, in institutions and elsewhere. Unpleasant and toxic volatile compounds evolved from biological wastes which are often contaminated with disease microorganisms are found on airplanes, buses, trains, and boats; in hospitals, nursing homes, restaurants, domestic bathrooms, kitchens and yards. In the home and elsewhere, carpets and other furnishings soiled by such biological wastes as vomit, animal feces, spoiled foods and urine also pose a problem, especially from the viewpoint of the noxious and toxic volatile organic and inorganic compounds they emit.
Extreme and expensive, yet only partially effective, measures are all that are currently available to deal with the VC and disease potential problems described above. For example, governmental regulations commonly require that the active site at a landfill be covered with six or more inches of dirt after each day's operations to seal in volatiles and to form a physical barrier which will keep disease vectors from contaminated wastes. As much as possible of this dirt is then removed the next working day, more waste is added, and the process is repeated.
Covering an irregular biowaste and trash surface with a layer of the requisite depth may be beyond the capability of even a conscientious heavy equipment operator, especially under adverse conditions where only a gluey clay or frozen soil may be all that is available. This approach cannot be employed when it is needed most--during prime daylight and working hours. Furthermore, it has the disadvantage of filling up landfills with dirt instead of wastes. Landfill sites are expensive; and communities, if not entire nations, are running out of sites to which their waste products can affordably be transported.
Other covers--tarpaulins and nets--are occasionally employed instead of dirt. Expensive, inconvenient and filthy from continued reuse, these covers are difficult to roll out and roll up each day. They do not last very long, are only somewhat effective and are more an indication of the seriousness of the problem than a solution to it. Like the dirt cover, the net or tarp offers no protection against or neutralization of VC's and disease vectors during working hours. Nets and tarps also become contaminated with septic liquids in or generated by decomposition of the biowaste. Nets simply add another site attractive to pests and disease vectors. Moreover, workers required to handle septic nets and tarps are at risk while the cost of landfill waste disposal is increased. Finally, nets and tarps, like dirt, become an additional waste disposal burden as they must ultimately be absorbed into the landfill.
Leachates pose a very significant environmental problem. Prevalent and widely publicized are the contamination of water tables and nearby streams, lakes and other bodies of water with leachates from landfills.
In newer landfills, the approach to solving the leachate problem has been to place an impervious polymeric liner in a basin or depression at the active site and dump the waste onto the liner. Leachates are drained from the liner into pools or ponds adjacent the landfill. These liquids are extremely noxious and toxic, a result mostly of the anaerobic processes dominant in a fill. The collected leachates are in most circumstances simply hauled away from the landfill and incinerated.
Commonly associated with these noisome leachates are also deleterious volatile organic compounds (VC's) and equally offensive inorganic gases and vapors. Profiles of the VC's commonly associated with leachates are very complex; but many noxious and toxic, gaseous sulphur and nitrogen compounds are invariably present. Leachates collected in landfill ponds and lagoons are accordingly a major source of atmospheric pollution.
Sewage treatment and other waste processing plants commonly employ more permanent leachate containments such as concrete sludge basins and dissolved air flotation cells, approaches not practical for landfills or for other disposal sites such as agricultural lagoons. Transport and incineration of leachates is expensive and merely serves to concentrate the noxious elements into more subtle but no less deadly oxidation products disseminated without treatment into the atmosphere.
In many circumstances, plastic bags with twist ties, containers with tight fitting lids and the like are employed to contain refuse, offgases and exuded liquids and to protect biowastes from pests and insects and other disease vectors with varying degrees of success. Bags and other containers only become a part of and do not solve the waste disposal problem because the containment does not reduce the amount of solid or liquid waste or offgases but simply stores these materials until the seal or barrier is broken in the collection, handling, disposal and other processing of the waste. Moreover, the breakdown of the stored waste by anaerobic processes can often proceed rapidly in the low oxygen environment of a waste storage container. It is generally accepted that anaerobic processes generate more noxious and toxic byproducts than aerobic processes do. So, to some extent, the solid waste disposal problem is ultimately worsened by use of storage containers. Isolating biowastes for handling and transportation to a disposal site is important but does not solve, only increases, the problems encountered at the waste disposal site.
Biowastes are collected and moved from the collection point to collection stations, then to the treatment and/or disposal site in or through such diverse receptacles as toilets, sewage pipes, the above-discussed plastic bags and garbage cans, and garbage trucks, to name only a few. Non-disposable waste collection and transportation containers including toilets, bedpans, garbage cans, dumpsters and the like can be cleaned to remove waste materials, a procedure which inherently minimizes the spread of these materials throughout the environment. Often employed for cleaning are aqueous solutions of commercial surfactants. If done properly, this approach is effective. However, it has the disadvantage of generating waste laden water, which in itself poses a significant waste disposal problem. Furthermore, in the collection, storage and transportation of biowastes, the common approach is to handle solid biowastes and liquid leachates together. Leaks and spillage and contamination of rolling stock are obvious and important drawbacks of this approach.
Aside from those discussed above, the disposal of biowastes has associated therewith the problem of controlling offensive odors emitted from the waste as it undergoes a variety of chemical reactions. Complexes commonly but inaccurately described as deodorants and usually comprised of volatile organic compounds have been used in attempts to compete with ubiquitous, noxious and toxic volatiles emitted from organic wastes. So-called deodorant bathroom sprays are widely available. And, at some landfills, the covering of the active site with a net at the close of each working day may be followed by the application of an aromatic complex to mediate the olfactory effects of malodorous volatile compounds.
The use of so-called deodorants for the purposes just described is at best of only limited effectiveness. Deodorants do not neutralize the inodorous but noxious volatile compounds commonly associated with malodors, and they deal with the malodor problem only through the questionable phenomenon of masking the offensive odor with a more acceptable one. Deodorants are expensive, tend to have a very limited if any real effectiveness and actually contribute to the problem by adding additional volatile compounds to those already existent in the problem area. Many biowastes contain significant concentrations of constituents with significant nitrogen, sulfur and other nutrient values. These potentially economically important constituents are routinely lost from biowastes because there is no practical process for preventing the loss of these values by volatization.
Instead, efforts have been limited to recovering products with nutritional and other values from the non-volatile components of biowastes. Among the traditional techniques and systems employed to treat and recover such products are digesters for sewage; dissolved air flotation cells for food and other process wastes; drying of fermentation byproducts, grains, and spent microorganisms; spray drying of whey; the drying or homogenizing of manure and fish into fertilizers; agricultural field spraying of livestock wastes; the recovery of pulps from the paper and vegetable and fruit processing industries; the manufacture of products such as particle board from wood and plant wastes and particles; offal rendering and composting.
One of the most valuable constituents of many biowastes is the water in which the biowaste solids are carried. Water is in very short supply in many regions of the world and is expensive. Currently, there are no viable methods for recovering and recycling this water, even for secondary (non-consumption) uses such as washdown; irrigation and operation of boilers, condensers, and cooling towers. Obviously lacking in waste disposal is a recovery technique which would be of considerable economic and other value to hard pressed and water short industries and to agriculturists.
With the exception of rendering, processes for recovering values from biowastes are essentially designed for controlling, handling and disposing of biowaste at as little cost as possible. The value of products actually recovered is very small compared to the product potential. Salvage processes do nothing to protect biowastes prior to or during processing; and they hasten evolution of volatiles, yielding products only after the majority of the damage to the original product and to the environment has been done.
Typical of the salvage processes in widespread use is composting. Composting has the drawback that it is a lengthy process--taking months to a year or more--, and space must be found for the compost pile for this extended period of time. Furthermore, the gases "belched off" as the compost is turned to provide adequate aeration contain much of the nutrient values in the decomposing organic materials. The resulting compost is a more-or-less inert humus with few if any beneficial constituents. Other potential values are lost to leachates formed and washed away during the composting process.
Agricultural spraying of livestock wastes is an example of another traditional biowaste salvage process. Though thought to be beneficial, this process actually increases pollution while reducing nutritional values potentially available from the biowaste. Typically, dairy wastes from clean-up and wash down of milking barns are collected in a pond or lagoon. The biowastes are loaded with valuable, biologically active microorganisms, enzymes and other digestive factors and partially digested or unspent nutrients which decompose as they are held in the containment area. Depending on conditions at this site, a multitude of noxious and toxic offgases and liquids are generated. Economically important materials are taken off in these offgases and exudates. These include values most needed as plant nutrients--nitrogen and sulfur.
Subsequent high pressure spraying forces stored gases out of the mixture, releasing the remaining values into the air as pollutants. The depleted waste reaching the soil and vegetation has little, if any, value. These immense losses to the soil and flora must be made up for with synthetic fertilizers and nutrients, representing a staggering and completely avoidable economic loss. Agricultural spraying of livestock wastes is also very wasteful of water. The concentration of water to solids in residues generated by washing down stalls, barns and the like is on the order of 95% water to 5% solids.
Current additives such as "polymers" (proprietary agglomerates) to the washdown water are not the answer. Additives used to enhance the concentration, compaction by dewatering, and separation of water borne animal wastes as well as waste waters from other industries either result in poor quality separations or alterations in the character of many waste constituents from potentially useable to toxic.
In short, there is currently lacking any technique or products for so treating biowastes as to: immobilize, neutralize or prevent the formation of noxious, toxic and even explosive volatiles and leachates; to more effectively compact biowastes and thereby make more effective use of waste processing systems and sites; to improve retention and recovery of potential economic values; to provide practical methods of insect, pest and disease vector control; to recover significant inherent values in the form of improved, traditional or new products or to improve pollution control in the collecting, treating, transporting and disposing of biowastes.